Method for the correction of spinal deformities through vertebral body tethering without fusion

ABSTRACT

A fusionless method of treating spinal deformities in the spine of a child or young adult involves attaching a tether to vertebral bodies on the convex side of the spine. Deformities are treated by using the tether to selectively constrain growth in a portion of the convex side of the spine. One device for tethering the spine is a combination of a strand threaded through channels defined in a set of blocks attached to the vertebral bodies on the convex side of the spine. Another device useful in the method is to attach spinal staples, preferably made of a shape memory alloy, to vertebral bodies, the staples spanning the intervertebral disc space.

[0001] This application is a continuation of pending U.S. patent application Ser. No. 09/421,207, filed on Oct. 20, 1999, which claims the benefit of U.S. Provisional Patent Application No. 60/130,909, filed on Apr. 23, 1999.

BACKGROUND OF THE INVENTION

[0002] Current operative methods for treating spinal deformities, particularly scoliosis, include correction of the curve by some internal fixation device, and fusion of the spine in the corrected state, which is typically accomplished by the placement of bone graft between adjacent vertebrae. This method of treatment is usually accomplished by way of posterior surgery, although anterior procedures are becoming more popular, as well as combinations of anterior and posterior procedures. Several instrumentation systems are available from various manufacturers to correct and stabilize the spine while fusion occurs. Among them are TSRH®, CD™, CD Hopf™, CD Horizon™, ISOLA™, Moss Miami and Synthes Universal Spine Systems. Nonoperative methods also exist and are used whenever applicable. These nonoperative methods include bracing and observation.

[0003] Juvenile idiopathic scoliosis typically occurs between the ages of 4 and 10 years. It can resolve spontaneously, respond to nonoperative therapy, or progress until fusion is required. Stapling across long bone physes has long been recognized as a predictable method of treating limb malalignment. Vertebral interbody stapling across the cartilaginous endplates and discs was attempted by Nachlas and Borden in a canine scoliosis model. Early human results in the 1950s were disappointing. Roaf reported limited successful correction of scoliosis by uninstrumented convex hemiepiphysiodesis. His study did not have a uniform patient population by skeletal maturity or scoliosis etiology.

[0004] Further shortcomings of current operative methods and devices are numerous. Patients with juvenile scoliosis who undergo curve stabilization with subcutaneous rods are subject to multiple surgical procedures for lengthening as they grow. Anterior and/or posterior spinal fusion in the skeletally immature patient often results in loss of vertebral body height and girth. Additionally, poor self-image may occur in adolescent patients who are externally braced for scoliosis. Moreover, curve stabilization with bracing is only successful in approximately 75% of patients. Another problem is that some children, while not currently candidates for a definitive fusion procedure, are likely to need such a procedure in the future. These would include children less than ten years of age, small in stature, premenstrual or riser two or lower, and those not physically able to tolerate the surgery required for a definitive fusion procedure. It would be preferable to eliminate the need for that procedure altogether.

[0005] Heretofore, there has been a need for an improved method of treating a spinal curvature. The present invention satisfies this need in a novel and non-obvious way.

SUMMARY OF THE INVENTION

[0006] In one form of the present invention, a method of treating a spinal curvature comprises constraining growth along a convex side of the spinal curvature.

[0007] In another form of the present invention, a method of treating a spinal curvature comprises constraining curve progression along a convex side of the spinal curvature.

[0008] In another form of the present invention, a method of treating a spinal curvature comprises attaching a longitudinal element to at least two vertebral bodies along a convex side of the spinal curvature.

[0009] One object of the present invention is to provide an improved method of treating a spinal curvature.

[0010] Further objects of the present invention will become apparent from the following description and illustrations.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011]FIG. 1 is a perspective view of a spinal staple according to one form of the present invention.

[0012]FIG. 2 is a front view of the spinal staple shown in FIG. 1.

[0013]FIG. 3 is a schematic illustration of one embodiment of the present invention, illustrating the spinal staple of FIG. 1 attached to vertebral bodies on a convex side of a spine.

[0014]FIG. 4 is a front view of a spinal staple according to another form of the present invention.

[0015]FIG. 5 is a bottom view of the spinal staple shown in FIG. 4.

[0016]FIG. 6 is a side view of the spinal staple shown in FIG. 4.

[0017]FIG. 7 is a rear view of the spinal staple shown in FIG. 4, and also illustrating an insertion configuration in phantom.

[0018]FIG. 8 is a front view of a spinal staple according to another form of the present invention.

[0019]FIG. 9 is a bottom view of the spinal staple shown in FIG. 8.

[0020]FIG. 10 is a side view of the spinal staple shown in FIG. 8.

[0021]FIG. 11 is a perspective view of the spinal staple shown in FIG. 8.

[0022]FIG. 12 is a rear view of the spinal staple shown in FIG. 8, and also illustrating an insertion configuration in phantom.

[0023]FIG. 13 is a schematic illustration of one embodiment of the present invention, illustrating the spinal staple of FIG. 4 attached to vertebral bodies on a convex side of a spine.

[0024]FIG. 14 is a front view of a spinal staple according to another form of the present invention.

[0025]FIG. 15 is a top view of the spinal staple shown in FIG. 14.

[0026]FIG. 16 is a side view of the spinal staple shown in FIG. 14.

[0027]FIG. 17 is a perspective view of the spinal staple shown in FIG. 14.

[0028]FIG. 18 is a rear view of the spinal staple shown in FIG. 14, and also illustrating an insertion configuration in phantom.

[0029]FIG. 19 is a schematic illustration of one embodiment of the present invention, illustrating the spinal staple of FIG. 14 attached to vertebral bodies on a convex side of a spine.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is hereby intended, such alterations and further modifications in the illustrated device, and such further applications of the principles of the invention as illustrated herein being contemplated as would normally occur to one skilled in the art to which the invention relates.

[0031] Various devices and surgical approaches are possible to implement the underlying idea of the present invention. Specifically, that idea is the correction of spinal deformities, particularly scoliosis, through fusionless tethering. In one form of the present invention, correction of the deformity is achieved by attaching a tether to the vertebral bodies on the convex side of the spine. The tether arrests or at least minimizes growth on the convex or “long” side of the spine, thereby allowing the concave or “short” side of the spine to grow and catch up with the long side. Alternatively, fusionless tethering may treat abnormal spinal alignment by simply preventing further misalignment such as curve progression.

[0032] A wide variety of surgical approaches may be used in implementing tethering of the convex side of the spinal curvature. One approach is an open thoracotomy (standard). Another surgical approach is a minimally invasive thoracoscopic approach (endoscopic). The surgical approach may also be a combined anterior/posterior approach (standard or endoscopic). However, it should be understood that the present invention can be practiced using other surgical approaches known to persons of ordinary skill in the art.

[0033] In any surgical approach used in practicing the invention, the tether used to selectively constrain growth will include at least one longitudinal element and one anchor element, with some type of an interconnection between the longitudinal element and the anchor element. In some cases, the longitudinal element and the anchor element may be one and the same. The following discusses generally some of the types of apparatus that may be used. Additionally, it should be understood that most, if not all, of the longitudinal elements or anchor elements may be manufactured from, but are not limited to, conventional implant metals, such as stainless steel or titanium. It should be further understood, and will be discussed in some detail for particular embodiments, that the longitudinal elements and anchor elements may take advantage of the shape memory and superelastic characteristics of shape memory materials including, for example, a shape memory alloy (“SMA”) such as, for example, nickel titanium.

[0034] Several devices are contemplated for spanning the longitudinal aspect of the spine during the fusionless tethering procedure. A list of potential longitudinal elements includes, but is not limited to, staples, cables, artificial strands, rods, plates, springs, and combinations of devices from the foregoing list. Details of each individual element will be discussed briefly.

[0035] The longitudinal element may be a spinal staple formed in a variety of shapes and sizes depending on its particular application. Staples may act as either the longitudinal element, the anchor element, or both. The staples may be manufactured from conventional implant metal, such as stainless steel or titanium. In one preferred embodiment, however, the staples are manufactured out of shape memory materials or alloys, such as, for example, nickel titanium to enhance fixation. One example of such an alloy is Nitinol sold by Memry Corporation of Menlo Park, Calif. Further details of preferred use, size, and material selection for the spinal staple may be found in copending U.S. patent application Ser. No. 09/421,903, entitled “Shape Memory Alloy Spinal Staple” and filed on Oct. 20, 1999.

[0036] Another possible selection for the longitudinal element is cabling. Prior spinal instrumentation involved the use of cables (e.g., Dwyer cables) in a fixation method for spinal fusion. However, this use of a cable never contemplated that a flexible cable could represent the longitudinal element in a fusionless tethering procedure.

[0037] The use of artificial or synthetic strands, much in the same way a cable could be used, may potentially add additional flexibility and motion to the fusionless tethering procedure. The artificial strand may be made of any suitable biocompatible material such as, for example, stainless steel, titanium or a polymer such as polyester or polyethylene. In one embodiment, the artificial strand may be manufactured from a braided polymer rope. In another embodiment, the artificial strand may be an adjustable spinal tether. Details of various embodiments of an adjustable spinal tether may be found in U.S. patent application Ser. No. 09/421,976, entitled “Adjustable Spinal Tether” and filed on Oct. 20, 1999. Such an artificial strand is preferably, but not necessarily, used in conjunction with an anchoring member to attach the artificial strand to the spine. Such anchoring members include, but are not limited to, screws and staples. It is also contemplated that the artificial strand may act as both the longitudinal element and the anchor by securing the artificial strand directly around the vertebrae to be tethered.

[0038] Another possible selection for the longitudinal element is a flexible rod. Such flexible rods could be manufactured of a small diameter and/or flexible material, such as, for example, a superelastic SMA. In a similar manner, a plate may be used as the longitudinal element. Such a plate could be configured with slots to allow sliding movement of other implants therein, such as, for example, a screw. Another possible choice for the longitudinal element is a spring. It should be understood that combinations of any or all of the above devices may be used as the longitudinal element for spanning the longitudinal aspect of the spine during the fusionless tethering procedure.

[0039] Most of the longitudinal elements discussed above, with the staples and artificial strands being possible exceptions, are anchored to the vertebral bodies by some type of anchor member to provide effective tethering. Several different types of anchors are contemplated as being within the scope of the invention.

[0040] As previously mentioned, a staple can serve as both an anchor as well as a longitudinal element since they possess the characteristics of both. As also mentioned, staples can be either of the conventional type or the SMA type. Also available for use in this capacity are scaled up suture-type anchor products. Such suture-type anchor products have been used as a means for affixing to soft, cancellous bone such as that found in a vertebral body. Additionally, screw down fixation plates, posts, etc. may be used as anchors.

[0041] Another potential anchor is an expandable screw. Examples include Mollie bolt type implants that are initially screwed into the vertebral body and expand by way of some type of expansion mechanism. Such an expansion mechanism may take advantage of the properties of shape memory materials to accomplish the expansion. Conventional screws and bone screws may also serve as anchors. Such screws may be coated with any number of osteoinductive or osteoconductive materials to enhance fixation.

[0042] The selection of longitudinal elements and anchor elements discussed above, as well as other longitudinal elements and anchor elements known in the art, provides a wide variety of interconnections. Once the anchor elements are in place, connection to the longitudinal elements can be governed by a number of different parameters. For example, the connection could be constrained or unconstrained, the anchor element could be allowed to slide along the longitudinal element or articulate with it as in the case of a ball joint, or may even float within a neutral zone. Several scenarios are envisioned.

[0043] One scenario involves constrained interconnection between the anchor elements and the longitudinal elements. Another possible scenario involves unconstrained interconnection between the anchor elements and the longitudinal elements in which no significant restriction exists between the longitudinal element and the anchor element. One example of such an unconstrained interconnection includes an artificial strand band around a post. Another example of such an unconstrained interconnection includes a screw extending through an artificial strand ribbon.

[0044] Still another interconnection scenario involves constrained end elements and unconstrained middle or inner elements. In this case, the construct would possess constrained interconnections between the end anchors and the longitudinal element with unconstrained interconnections in between. The unconstrained interconnections could employ either a sliding arrangement or a ball joint arrangement. Another interconnection scenario employs ball joint interconnections. Ball joints represent a semi-constrained situation in which the anchor is prevented from sliding along the longitudinal element, but can articulate within some spherical range of motion relative to the longitudinal element. It should be understood that combinations of any or all of the above interconnection scenarios may be used in practicing the present invention.

[0045] The above disclosure sets forth a broad range of devices and concepts envisioned for fusionless tethering of spinal deformities. The specifics with regard to the methods of treatment are similarly broad. Notably, a wide range of spinal deformities may be treated by the disclosed devices and methods. The primary indications for treatment will be progressive idiopathic scoliosis, with or without sagittal deformity, in either infantile or juvenile patients. The preferred patient population upon which to practice the present invention is prepubescent children (before growth spurt) less than ten years old. Other patient groups upon which the present invention may be practiced include adolescents from 10-12 years old with continued growth potential. It should be understood that the present invention may also be used on older children whose growth spurt is late or on older children with retained growth potential. It should be further understood that the present invention may also be used in preventing or minimizing curve progression in individuals of various ages.

[0046] Generally, in the case of scoliosis, tethering will take place on the convex side of the curve. An anterior, minimally invasive (thoracoscopic) procedure can be carried out on the convex side of the spinal curve in order to prevent continued growth on that side of the curve. As the pre-growth spurt child approaches puberty, the untethered side of the spine will grow unconstrained, ultimately eliminating the curvature of the spine in the frontal plane. It is preferable to deliver this method of treatment in a minimally invasive approach using thoracoscopic instrumentation. It is contemplated as being within the scope of the invention, however, that open use of these systems may be appropriate in some cases. It is further contemplated as being within the scope of the invention that the procedure may be posterior as well as anterior, or a combination of both. Finally, it should be understood that if the procedure fails to correct the curve, but does in fact prevent further progression (which includes increase in the magnitude of the curve), it can and should be considered a successful treatment.

[0047] In one embodiment of the present invention, fusionless correction of scoliosis is achieved by thoracoscopically placing shape memory alloy staples into the vertebral bodies on the convex side of the spine. The staples will span the intervertebral space and act as a tether on the spine. This tether will arrest growth on the convex (“long”) side of the spine and allow the concave (“short”) side of the spine to grow and catch up with the long side. Once correction is achieved, the staple may be removed thoracoscopically if desired. The removal of the staples permits further growth of the vertebral bodies. It should be understood that the stapling method is equally applicable in non-endoscopic procedures. It should be further understood that the staples may be made of a conventional implant metal such as titanium or stainless steel.

[0048] The following contraindications for use of thoracoscopically assisted spinal stapling should be noted: (1) inability to wear an orthosis postoperatively, (2) greater than 40 degree kyphosis, (3) medical contraindication to general anesthetic, (4) pulmonary function which would contraindicate intraoperative collapse of the convex lung, and (5) scoliosis deformity where three or more disc spaces are not accessible to thoracoscopically assisted vertebral interbody stapling. It should be understood, however, that the presence of any or all of the above mentioned contraindications does not preclude the potential utility of spinal stapling and/or vertebral body tethering.

[0049] The general details of one embodiment of a surgical technique according to one form of the present invention will now be described. General anesthesia is utilized. A double lumen endotracheal tube is inserted with the possible assistance of fiberoptic visualization. The convex lung is collapsed. A general or vascular surgeon familiar with endoscopic surgery in the thorax may be used as an assistant. The patient is positioned in the lateral decubitus position with the convex side of the scoliosis spinal curvature in the up position. The table is not flexed. Five vertebrae (four intervertebral discs) are stapled. Specifically, the apical vertebral body, the two vertebrae proximal, and the two vertebrae distal are treated. Three endoscopic ports are utilized. The first port is anterior and positioned over the apex of the scoliosis spinal curvature. The second and third ports are positioned in the posterior auxiliary line with the second port being centered over the second vertebrae of the five being treated and the third port being centered over the fourth vertebrae being treated. The endoscope is maintained in the first port and a fan retractor is placed in the second port. An anterior-posterior (AP) radiograph is used to confirm the levels. The parietal pleura is not excised and the segmental vessels are avoided.

[0050] A number of general surgical instruments may also be used in the procedure, along with the following system specific implants and instruments. The main implant is, of course, a spinal staple, preferably manufactured from a shape memory material. The size of the staple will vary depending on the size and number of the vertebral bodies to be spanned. The instruments used during the procedure may include: a staple awl, a staple opener, a straight staple inserter, an angled staple inserter, a staple impactor, and/or a staple extractor.

[0051] Pilot holes are made using the staple awl and are located anterior to the midbody of the vertebrae. The staple awl is inserted part way and position is checked with either x-ray or image intensifier. Prior to removal of the staple awl from the pilot holes, an electric cauterizer (Bovie) can be placed in contact with the endcap of the staple awl to minimize bleeding from the pilot holes. In one preferred embodiment, two sets of pilot holes are made at each level to accommodate two staples per disc space. Two staples are then placed spanning each disc space. The first staple is loaded into either a straight staple inserter or an angled staple inserter. The staple is then placed into the pilot holes made by the staple awl. The inserter may be tapped with a mallet to facilitate placement of the staple. The staple is then released from the inserter and the instrument is removed. If further seating of the staple is required, a staple impactor may be used in conjunction with a mallet for final seating of the staple into the vertebral bone. The aforementioned steps are then repeated for the next staple. It should be understood, however, that tethering may also be accomplished with just one staple spanning each disc space instead of two staples. It should also be understood that the use of more than one staple allows for correction of spinal curvature in more than one plane.

[0052] The instruments in the second and third ports are switched and the remaining two discs are stapled. The wounds are closed and a ten or twelve gauge chest tube is inserted and later withdrawn at twenty-four hours postop. The chest tube is used to prevent pneumothorax since there is no hemothorax. Once the endoscope is in place, the remainder of the procedure seldom takes more than one hour. Hospitalization is usually for two to three days.

[0053] Apical vertebral interbody stapling theoretically affords immediate and reversible fixation of the anterior vertebral physes. Thoracoscopic insertion minimizes damage to surrounding tissues and permits placement of multiple staples to allow curve correction in more than one plane.

[0054] With reference to FIGS. 1 and 2, shown therein is one embodiment of a spinal staple 100 that may be used in association with the present invention. Staple 100 is generally U-shaped and is comprised of a crossbar 101 extending between legs 102 and 103. Staple 100 has an inner surface 110 and an outer surface 120. Leg 102 has a pointed tip 104 and leg 103 has a pointed tip 105 for insertion into vertebral bodies. It should be understood that tips 104, 105 may take on a variety of configurations. Leg 102 has barbs 106 on inner surface 110 and barbs 107 on outer surface 120. Similarly, leg 103 has barbs 108 on inner surface 110 and barbs 109 on outer surface 120. Barbs 106, 107, 108, and 109 aid in the prevention of staple backout. Additionally, having barbs on both inner surface 110 and outer surface 120 of each leg 102, 103 of staple 100 allows the use of shorter barbs in the direction transverse to the longitudinal axis of each leg. It should be understood, however, that each leg 102, 103 may have barbs on the inner surface 110 or outer surface 120.

[0055] It should be noted that in one preferred embodiment, crossbar 101 and legs 102 and 103 all have a nearly elliptical profile obtained by truncating a circular cross-section. A staple design with an elliptical or near elliptical crossbar 101 is helpful in controlling rotation of the staple 100 and permits some assistance in staple removal. It should be understood, however, that the profile of legs 102, 103 and crossbar 101 may take on configuration other than elliptical, such as, for example, a circular cross-section. It should also be understood that legs 102, 103 and connecting portion 101 may have different profiles. It should additionally be understood that staple 100 may be made of commercially pure titanium, some other conventional implant metal, or an SMA.

[0056] While details of several embodiments of a spinal staple are discussed in the copending application titled “Shape Memory Alloy Spinal Staple,” some general points are reviewed here for convenience. The staples are preferably made of Nitinol, a biocompatible, shape memory metal alloy of titanium and nickel. Such staples are capable of being bent when cooled and reformed to their original shape when reheated. It is also possible to take advantage of the shape memory alloy's ability to transform from its austentic state to a stress induced martensitic state. The metal changes shape with temperature or under the influence of stress because of crystalline phase changes. Thus a staple made of a SMA can be inserted in two different ways as desired.

[0057] In one embodiment, the SMA staple is cooled and then deformed while at a temperature less than the transformation temperature at which it is in the martensitic phase. The staple is then inserted in its deformed shape and when heated will reform to its original shape. In a second embodiment, the staple is deformed and inserted while held in the deformed state. However, in the second embodiment, the SMA is selected to have a temperature transformation range such that the staple undergoes a transition from austenite to stress-induced martensite under the influence of the deformation forces. Thus, when the staple of the second embodiment is inserted and released, it is already at a temperature such that it automatically attempts to reform toward its original shape.

[0058] The SMA's properties at the higher temperature (austenite phase) are similar to those of titanium. The temperature at which the staple will undergo the shape transformation can be controlled by the manufacturing process and the selection of the appropriate alloy composition. Injury to the surrounding tissues should be negligible if the transformation temperature is at or near body temperature. There is minimal threat of thermal injury to the spinal cord or nerves, or adjacent vascular structures. Nitinol has a very low corrosion rate and has been used in a variety of medical implants (e.g., orthodontic appliances and stents). Implant studies in animals have shown minimal elevations of nickel in the tissues in contact with the metal. The levels of titanium are comparable to the lowest levels found in tissue near titanium hip prostheses.

[0059] With reference to FIG. 3, shown therein is a plurality of spinal staples 100 anchored in adjacent vertebral bodies 60. Specifically, the legs 102, 103 are driven into adjacent vertebral bodies 60 with the crossbar 101 spanning the intervertebral disc space 61. As should be appreciated, the staples 100 are used in accordance with one embodiment of the present invention to constrain growth and/or curve progression along a convex side of the spinal curvature.

[0060] With reference to FIGS. 4-7, shown therein is another embodiment of a spinal staple 200 that may be used in association with the present invention. Although staple 200 is preferably formed of a shape memory material, it should be understood that staple 200 may also be formed of commercially pure titanium or some other conventional implant metal. Staple 200 is generally unshaped and is comprised of a cross bar 201 extending between legs 202 and 203. Staple 200 has an inner surface 210 and an outer surface 220. Leg 202 has a pointed tip 204 and leg 203 has a pointed tip 205 for insertion into the vertebral bodies. It should be understood that tips 204, 205 may take on a variety of configurations. The back of staple 200 has a plurality of notches 221 for final seating of the staple into the bone or vertebrae. Notches 221 aid the surgeon in independently driving each tine or leg 202, 203 as necessary (see FIG. 13).

[0061] With specific reference to FIG. 7, the deformed martensitic insertion shape of the legs 202, 203 of staple 200 is shown in phantom. It should be understood that this deformed state may arise from the formation of martensite because of temperature conditions or the formation of stress induced martensite from the application of a force. After the staple is inserted in its open position, either the stress is released or the staple is heated to reform the staple to its memorized closed shape.

[0062] With reference to FIGS. 8-12, shown therein is another embodiment of a spinal staple 300 that may be used in association with the present invention. Although staple 300 is preferably formed of a shape memory material, it should be understood that staple 300 may also be formed of commercially pure titanium or some other conventional implant metal. Staple 300 is generally unshaped and is comprised of a cross bar 301 extending between legs 302 and 303. Staple 300 has an inner surface 310 and an outer surface 320. Leg 302 has a pointed tip 304 and leg 303 has a pointed tip 305 for insertion into the vertebral bodies. It should be understood that tips 304, 305 may take on a variety of configurations. The back of staple 300 has a plurality of notches 321 for final seating of the staple into the bone or vertebrae. Notches 321 aid the surgeon in independently driving each tine or leg 302, 303.

[0063] With specific reference to FIG. 12, the deformed martensitic insertion shape of the legs 302, 303 of staple 300 is shown in phantom. It should be understood that this deformed state may arise from the formation of martensite because of temperature conditions or the formation of stress induced martensite from the application of a force. After the staple is inserted in its open position, either the stress is released or the staple is heated to reform the staple to its memorized closed shape.

[0064] With reference to FIG. 13, shown therein is a plurality of spinal staples 200 anchored in adjacent vertebral bodies 60. Specifically, the legs 202, 203 are driven into adjacent vertebral bodies 60 with the crossbar 201 spanning the intervertebral disc space 61. As should be appreciated, the staples 200 are used in accordance with one embodiment of the present invention to constrain growth and/or curve progression along a convex side of the spinal curvature. In this particular embodiment, the spinal staples 200 have notches 221 to aid in the final seating of the staple into bone. This allows the surgeon to drive each leg 202, 203 independently as necessary. It should be understood that spinal staple 300 may be used in a manner similar to that of spinal staple 200.

[0065] With reference to FIGS. 14-18, shown therein is another embodiment of a spinal staple that may be used in association with the present invention. Although staple 400 is preferably formed of a shape memory material, it should be understood that staple 400 may also be formed of commercially pure titanium or some other conventional implant metal. Staple 400 has four prongs or tines 402, 404, 406, 408 having pointed tips 403, 405, 407, and 409, respectively. However, it should be understood that staple 400 could include any number of prongs, including a pair of prongs. The legs 402, 404, 406, 408 are interconnected by a cross plate 401. The staple 400 is symmetrical about the imaginary axis 415 that bisects the width of the staple 400. Crossbar or cross plate 401 has a bore 450 defined therein extending between outer surface 420 and inner surface 410. The bore 450 is defined by a tapered insertion surface 460 adjoining a surface 461 generally parallel to the axis 415. Bore 450 is intended to receive a fastener, such as, for example, a screw or a bolt. The fastener may be attached to other fasteners received in the bores of other staples by an artificial strand or adjustable tether such as those previously described in the application entitled “Adjustable Spinal Tether.”

[0066] With specific reference to FIG. 18, the deformed martensitic insertion shape of the legs 402, 404, 406, 408 of staple 400 is shown in phantom. It should be understood that this deformed state may arise from the formation of martensite because of temperature conditions or the formation of stress induced martensite from the application of a force. After the staple is inserted in its open position, either the stress is released or the staple is heated to reform the staple to its memorized closed shape.

[0067] With reference to FIG. 19, shown therein is a plurality of spinal staples 400 anchored in adjacent vertebral bodies 60. Specifically, the legs 402, 404, 406, 408 are driven into adjacent vertebral bodies 60 with the crossbar 401 spanning the intervertebral disc space 61. As should be appreciated, the staples 400 are used in accordance with one embodiment of the present invention to constrain growth and/or curve progression along a convex side of the spinal curvature.

[0068] It should be understood that any of the features present in the above-discussed spinal staple embodiments may be interchanged to form other embodiments of spinal staples. For example, staples 200, 300 and 400 may include barbs formed on the staple legs. Additionally, staples 100 and 500 may include notches formed on the back of the staple cross bar. Moreover, staples 100, 200 and 300 may include more than two prongs. It should be further understood that any of disclosed methods of treatment may entail the use of one, two, or even more than two spinal staples at each vertebral level to be treated.

[0069] While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered illustrative and not restrictive in character, it being understood that only the preferred embodiments have been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected. 

What is claimed:
 1. A fusionless method of treating abnormal alignment of a spine, the spine having a convex side and a concave side, the method comprising the steps of: attaching a tether to at least two vertebral bodies of the spine; and constraining curve progression in a portion of the convex side of the spine.
 2. The method of claim 1, further comprising the step of removing the tether after treatment of the abnormal alignment.
 3. The method of claim 2, wherein the tether is removed during an open thoracotomy surgical approach.
 4. The method of claim 2, wherein the tether is removed during a minimally invasive thoracoscopic surgical approach.
 5. The method of claim 2, wherein the tether is removed during a combined posterior/anterior surgical approach.
 6. The method of claim 1, wherein the tether includes a longitudinal element anchored to a vertebral body.
 7. The method of claim 6, wherein the longitudinal element is a strand and the anchor includes a metal device fixed to the vertebral body and the attachment step connects the strand to the anchor.
 8. The method of claim 1, wherein the tether includes at least one staple and attaching the staple includes stapling the staple into at least one vertebral body on the convex side of the spine.
 9. The method of claim 8, wherein the staple is positioned on an anterior aspect of the spine.
 10. The method of claim 8, wherein the stapling is vertebral interbody stapling so that the staple spans at least one disc separating the vertebral bodies.
 11. The method of claim 8, wherein the staple has at least two prongs.
 12. The method of claim 8, wherein the staple is manufactured from a shape memory alloy.
 13. The method of claim 12, wherein the staple is attached to the vertebral body at a temperature lower than the transformation temperature.
 14. The method of claim 1, wherein constraining includes attaching the tether so as to minimize growth on the convex side of the spine and allow growth on the concave side of the spine.
 15. The method of claim 1, wherein the tether is an adjustable length spinal tether configured into a loop positioned around anchor points located on the convex side of the spine.
 16. A fusionless method of correcting deformities in a spine, the spine having a convex side and a concave side, the method comprising the steps of: attaching a tether to at least two vertebral bodies of the spine; and selectively constraining growth of the convex side of the spine.
 17. The method of claim 16, further comprising the step of removing the tether after correction of the deformity.
 18. The method of claim 17, wherein the tether is removed during an open thoracotomy surgical approach.
 19. The method of claim 17, wherein the tether is removed during a minimally invasive thoracoscopic surgical approach.
 20. The method of claim 17, wherein the tether is removed during a combined posterior/anterior surgical approach.
 21. The method of claim 16, wherein the tether includes a longitudinal element anchored to a vertebral body.
 22. The method of claim 21, wherein the longitudinal element is a strand and the anchor includes a metal device fixed to the vertebral body and the attachment step connects the strand to the anchor.
 23. The method of claim 16, wherein the tether includes at least one staple and attaching the staple includes stapling the staple into at least one vertebral body on the convex side of the spine.
 24. The method of claim 23, wherein the staple is positioned on an anterior aspect of the spine.
 25. The method of claim 23, wherein the stapling is vertebral interbody stapling so that the staple spans at least one disc separating the vertebral bodies.
 26. The method of claim 23, wherein the staple has at least two prongs.
 27. The method of claim 23, wherein the staple is manufactured from a shape memory alloy.
 28. The method of claim 27, wherein the staple is attached to the vertebral body at a temperature lower than the transformation temperature.
 29. The method of claim 16, wherein constraining includes attaching the tether so as to arrest growth on the convex side of the spine and permit growth on the concave side of the spine.
 30. The method of claim 16, wherein the tether is an adjustable length spinal tether configured into a loop positioned around anchor points located on the convex side of the spine. 